Polyacrylamide Adsorption from Aqueous Solutions on Gold and Silver Surfaces Monitored by the Quartz Crystal Microbalance

Abstract

Viscoelastic properties of ultrathin films are important in such applications as polymer-supported lipid bilayers, and the quartz crystal microbalance (QCM) offers the ability to measure these properties in situ. In this study, polymer films are created by adsorbing polyacrylamide to gold and silver surfaces from aqueous solutions. The molecular weight of the polymers ranges from 10 000 to 1 000 000 g/mol, and concentrations range from dilute to the overlap concentration. Using a continuum mechanics viscoelastic film model, we extract film property parameters from frequency and dissipation change measurements for multiple harmonics. The precision of the QCM and the modeling technique are limited, however, leading to large property value ranges for any given film. The adsorbed films range from 10 to 150 Å thick, with moduli ranging from 15 to 228 kPa and viscosities ranging from 1.21 × 10-3 to 2.85 × 10-3 Pa s. Meanwhile, the bulk solution properties of the different molecular weight materials lead to drastically different adsorption profiles. While the viscosity differences between water and 10 000 M w polymer solutions lead to large frequency and dissipation responses, the large relaxation times of 1 000 000 M w polymers make their bulk solution viscosity differences from water largely undetectable by the QCM. In addition, the viscosity of the 10 000 M w solutions may be frequency dependent over the range of operating frequencies, contrary to the standard QCM assumption of frequency independence.

Adsorption of fatty acids from alkane solution studied with quartz crystal microbalance

“…To calculate the true sensed mass, taking into account any effect of the viscoelastic properties of the adsorbed layer, the equivalent mass was calculated using equation (4) for the different harmonics. The frequency shifts obtained after correcting for bulk effects as described above were used as df in equation (4).…”

“…The frequency shifts obtained after correcting for bulk effects as described above were used as df in equation (4). The true sensed mass obtained is shown as triangles in figures 2-4.…”

“…In the 1980s theories were developed that showed that the technique could also be used in fluids, and since then the QCM has found use in an increasing number of research fields. Nowadays the QCM is used to study, among other things, adsorption of surfactants from aqueous solutions [1,2], adsorption and swelling of polymer layers [3][4][5], viscoelastic properties of for example polymers [6,7], deposition of vesicles [8,9], and coadsorption of surfactant and polymers [10].…”

Characterization of Matrigel interfaces during defined human embryonic stem cell culture

“…In this experiment F1 and D1 were ignored as they were not reliable. 20,21 Frequency and dissipation values were recorded in air for all crystals. All liquids were allowed to reach room temperature before introduction into the QCM-D chamber, which was set to 25°C.…”

Effect of a Non-Newtonian Load on SignatureS2for Quartz Crystal Microbalance Measurements

“…QCM applications have been extended to measure viscoelastic macromolecular interactions with the surfaces of fluids including natural and synthetic macromolecules such as DNA [5,6], proteins [7,8], microorganisms [9], endothelial cells [10], polymers [11][12][13], and polyelectrolyte multilayers [14]. Through these studies, QCM measurements have shown that viscoelastic fluids containing macromolecules exhibit different behavior from that of Newtonian fluids.…”